Parkinson's disease (PD) is the fourth most common neurological disease among the elderly in the United States. An estimated 75% to 100% of adults with PD develop speech and voice problems that impair their communication skills. While a variety of speech therapeutic techniques are used to help improve their communication skills, treatment has shown limited improvement over time. One factor that complicates treatment efficacy is that PD is characterized by a variety of physiological phenomena that may affect speech production. Also, researchers still do not understand the precise processes in the brain that underlie their speech deficits. The purpose of this proposal is to examine vowel production in individuals with PD. By having them produce vowels under a variety of conditions will provide an opportunity to examine at least three logically separable aspects of speech motor control that may underlie speech disorders In PD. The processes we shall examine will include: (1) open-loop control of vowel production; (2) the consistency of motor impairment on vowel production (i.e., vowel space); and (3) the ability to achieve motor equivalence of the tongue and lips during jaw perturbation. The results from this study will be important because they will help broaden our knowledge of the underlying processes that contribute to speech problems in PD. [unreadable] [unreadable]